SYNCHROTRON RADIATION PHOTOELECTRON STUDY OF HEUSLER-TYPE Fe2VAl-BASED ALLOYS

The electronic structures of Heusler-type Fe2VAl-based alloys, n-type thermoelectric alloys Fe2VAl1-zXz(X = Si, Ge) and p-type one Fe2(V1-yTiy)Al, have been investigated by photoelectron spectroscopy with use of synchrotron radiation as an excitation photon source. Observed valence-band spectra of Fe2VAl agree quite well with the predicted density of states with a sharp pseudogap across the Fermi energy EF. Small substitution in Fe2VAl1-zXz and Fe2(V1-yTiy)Al reveals a rigid-band-like energy shift of the valence band, although the observed shift is smaller than expected in the rigid band model. Further substitution causes the modification of the electronic structure near EF and the appearance of mid-pseudogap states. However, the dependence of the thermoelectric properties of these alloys on substitution can be qualitatively explained by the observed change in the electronic structure near EF.